Wnt signaling induces proliferation of sensory precursors in the postnatal mouse cochlea
Wnt signaling induces proliferation of sensory precursors in the postnatal mouse cochlea
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DOI：
10.1073/pnas.1202774109
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发表时间：
2012-05-22
影响因子：
11.1
通讯作者：
Cheng, Alan G.
中科院分区：
文献类型：
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作者：
Chai, Renjie;Kuo, Bryan;Cheng, Alan G.
内耳毛细胞是对听觉功能至关重要的特殊感觉细胞。先前的研究表明，感觉上皮是有丝分裂后的，但它含有可以在体外表现为祖细胞的细胞，包括形成新毛细胞的能力。Lgr 5是Wnt靶基因，标志着新生儿耳蜗中不同的支持细胞类型。在这里，我们测试了Lgr 5（+）细胞是Wnt反应性感觉前体细胞的假设。与其静止的体内行为相反，通过流式细胞术从新生Lgr 5（EGFP-CreERT 2/+）小鼠分离的Lgr 5（+）细胞增殖并形成克隆集落。培养10 d后，新的感觉细胞形成并显示特定的毛细胞标记物（myo 7a，calretinin，parvalbumin，myo 6）和表达F-actin和espin的静纤毛样结构。与其他支持细胞相比，Lgr 5（+）细胞是myo 7a（+）细胞的富集前体细胞，其中大多数形成时没有分裂。用Wnt激动剂治疗增加了增殖和集落形成能力。相反，Wnt信号传导的小分子抑制剂抑制增殖而不损害通过直接分化形成的myo 7a+细胞。体内谱系追踪支持Lgr 5+细胞在新生儿Lgr 5（EGFP-CreERT 2/+）耳蜗中产生myo 7a（+）毛细胞的想法。此外，β-连环蛋白的过度表达引发了耳蜗感觉上皮细胞内Lgr 5（+）细胞的增殖和短暂扩增。这些结果表明，Lgr 5标记感觉前体，Wnt信号可以促进它们的增殖，并在感觉器官发育过程中提供对Wnt响应祖细胞的机制见解。
Inner ear hair cells are specialized sensory cells essential for auditory function. Previous studies have shown that the sensory epithelium is postmitotic, but it harbors cells that can behave as progenitor cells in vitro, including the ability to form new hair cells. Lgr5, a Wnt target gene, marks distinct supporting cell types in the neonatal cochlea. Here, we tested the hypothesis that Lgr5(+) cells are Wnt-responsive sensory precursor cells. In contrast to their quiescent in vivo behavior, Lgr5(+) cells isolated by flow cytometry from neonatal Lgr5(EGFP-CreERT2/+) mice proliferated and formed clonal colonies. After 10 d in culture, new sensory cells formed and displayed specific hair cell markers (myo7a, calretinin, parvalbumin, myo6) and stereocilia-like structures expressing F-actin and espin. In comparison with other supporting cells, Lgr5(+) cells were enriched precursors to myo7a(+) cells, most of which formed without mitotic division. Treatment with Wnt agonists increased proliferation and colony-formation capacity. Conversely, small-molecule inhibitors of Wnt signaling suppressed proliferation without compromising the myo7a+ cells formed by direct differentiation. In vivo lineage tracing supported the idea that Lgr5+ cells give rise to myo7a(+) hair cells in the neonatal Lgr5(EGFP-CreERT2/+) cochlea. In addition, overexpression of beta-catenin initiated proliferation and led to transient expansion of Lgr5(+) cells within the cochlear sensory epithelium. These results suggest that Lgr5 marks sensory precursors and that Wnt signaling can promote their proliferation and provide mechanistic insights into Wnt-responsive progenitor cells during sensory organ development.